1. Field of the Invention
The present invention relates to compositions suitable for use in cleaning hard surfaces, particularly the hand washing of dishes.
2. Description of the Prior Art
Detergent compositions are formulated to provide as many consumer recognizable benefits as possible while minimizing the consumer recognizable negatives.
A detergent composition used to clean dishes or other food-soiled hard surfaces must first be effective in cleaning the soiled surface. Secondly, it is desirable that the detergent composition be mild to human skin if the product is to be used for hand dishwashing.
Alkyl sulfates and alkyl benzene sulfonates have frequently been used in liquid hand dishwashing compositions as the surface active agent of the composition. While these materials are very effective in cleaning food-soiled surfaces, they are undesirable from the standpoint that they may cause a harsh, reddened appearance to the skin when used at high concentrations or where the consumer's hands are exposed for prolonged periods of time to the dishwater containing these surface active agents.
It was proposed in U.S. Pat. No. 3,793,233, issued Feb. 19, 1974 to Rose et al, that the harshness of alkyl sulfates could be reduced by incorporation of high ethoxylate content alkyl ethoxy sulfates at a ratio of from about 2:1 to about 6:1 to the alkyl sulfate. The degree of ethoxylation of the alkyl ethoxy sulfate in the Rose et al patent is stated to be from about 5 to about 12 moles of ethylene oxide per mole of the alkyl ethoxy sulfate. The mainstay surface active agent in the Rose et al patent is, however, the alkyl sulfate as the alkyl ethoxy sulfates at the aforementioned levels of ethoxylation are not particularly effective surface active agents for the cleaning of soiled dishes.
To improve the performance of alkyl benzene sulfonates, it has been proposed in U.S. Pat. No. 3,231,504 to Marion et al, issued Jan. 25, 1966, that alkyl benzene sulfonates be combined with alkyl ethoxy sulfates at a respective weight ratio of from about 6.5:1 to about 1:4, and contains as an additional component, a water-soluble inorganic builder salt. The alkyl ethoxy sulfates used to improve the performance of the Marion et al composition are stated to have an alkyl chain length of from 10 to 18 carbon atoms, and a degree of ethoxylation of about 2 to 15, preferably 3 to 8 moles of ethylene oxide per mole of alkyl ethoxy sulfate.
Alkyl ethoxy sulfates of low ethoxy content have been used as the primary anionic detergent active primarily for their ability in cleaning rather than as a mildness additive with other anionic or nonionic detergent components. U.S. Pat. No. 3,179,598 issued to Smith, Apr. 20, 1965, teaches a detergent composition containing from about 20% to 40% by weight of an alkyl ethoxy sulfate wherein the alkyl portion is a straight chain radical having from about 10 to 14 carbon atoms wherein at least 50% of the alkyl groups have 12 carbon atoms and the degree of ethoxylation is between 0 and 4. These alkyl ethoxy sulfates are used in combination with a trialkyl (tertiary) amine oxide, having one straight chain alkyl group with from 10 to 14 carbon atoms and two short chain alkyl groups having 1 or 2 carbon atoms. The ratio of the alkyl ethoxy sulfate in the Smith patent to the amine oxide is from about 3:1 to about 7:1. In U.S. Pat. No. 3,179,599, issued to Eaton and Gebhardt on Apr. 20, 1965, an alkyl ethoxy sulfate is again used as the primary anionic surface active agent in combination with a tertiary amine oxide both having the description given in the Smith patent, supra, and as an additional component, and alkyl glyceryl ether sulfonate having from about 10 to 14 carbon atoms.
The improvement of the Eaton and Gebhardt patent over that of Smith is stated to be in the addition of the alkyl glyceryl ether sulfonate which lowers the sudsing sensitivity of the combination of the alkyl ether sulfate and the amine oxide under acidic conditions. Sudsing, that is the ability of a dishwashing composition to generate and maintain an adequate suds level during use is an important variable in such compositions. Consumers have for years related the cleaning ability of soaps and synthetic detergents to their ability to generate and maintain copious amounts of suds in the wash solution. Moreover, consumers have been unwilling to accept liquid dishwashing compositions which do not provide such sudsing characteristics. Thus, in order to meet consumer aesthetics, it is necessary to prepare a detergent composition which is not only effective in cleaning and mild to the skin but which also generates and maintains an adequate suds level in the wash water.
Whereas, Eaton and Gebhardt were concerned with the pH of the wash solution and its relationship to the generation and maintenance of adequate suds levels, it has been stated in U.S. Pat. No. 3,332,878 to Coward et al issued July 25, 1967, that small amounts of the water-soluble salts of magnesium and calcium such as those of the sulfate and chloride ions, may be added to the liquid detergent composition to provide increased suds stability during usage of the product. The addition of the water-soluble salts taught by Coward et al and those disclosed in South African Patent Application 68/4594; namely, copper, iron, zinc and aluminum salts, while providing increased suds stability, are very detrimental to the initial suds generation over a wide range of water hardness.
Tuvell et al in U.S. Pat. No. 3,775,349 issued Nov. 27, 1973, discloses that mixtures of alkyl sulfates and alkyl alkoxy sulfate detergents perform better if large quantities of the alkyl radical are decyl.
A more particular description of the alkyl sulfate and alkyl alkoxy sulfate detergents described in the Tuvell et al. patent provides that the alkyl radical should have from 10 to 20 carbon atoms wherein about 10% to 50% of the alkyl groups are decyl and the alkoxy moiety is either an ethoxy or isopropoxy radical averaging from 2 to 4 moles of alkoxy per mole of alkyl alkoxy sulfate. The Tuvell et al. patent states that other adjuvants may be used in combination with the alkyl alkoxy sulfates such as tertiary amine oxides, alkyl benzene sulfonates and fatty acid ethanol amides.
Tuvell et al while disclosing that a high concentration of decyl radicals are desirable in a dishwashing composition, does so in the context that large amounts of decyl sulfates are present and are used to lower the average ethoxylate content to the claimed range of from 2 to 4 alkoxy units per decyl radical. While the decyl sulfates are useful in cleaning food-soiled surfaces, they are eminently harsh to human skin -- such that prolonged exposure can lead to cracked and chapped, reddened hands. The decyl alkoxy content average of from 2 to 4 moles per decyl unit has a tendency to reduce the skin irritation caused by the unalkoxylated decyl sulfate. However, in order to achieve the average alkoxy content taught by Tuvell et al a large amount of alcohol alkoxylated sulfates of higher than four alkoxy units must be used and cleaning performance is substantially diminished.
It has now been found that a liquid detergent composition which is particularly effective in cleaning dried-on food soils is prepared using a mixture of decyl alcohol alkoxy sulfate having a mean alkoxy content of from about one to about four wherein a specified minimum percentage of the mono-alkoxylate is present in the composition.
It is thus an object of the present invention to prepare a liquid detergent composition which is effective in the removal of food soils.
It is another object of the present invention to provide a detergent composition which while being eminently effective in the removal of food soils, exhibits decreased harshness to the skin.
It is yet a further object of the present invention to prepare a detergent composition which provides adequate initial suds generation over a range of water hardness.
A further object of the present invention is to provide a detergent composition with increased suds stability over a range of water hardness.
It is still yet another object of the present invention to provide a detergent composition which is effective in cleaning, mild to the skin, and which at the same time provides adequate initial suds generation and suds stability during the wash, even upon the addition of substantial amounts of hardness ion to the composition.
Throughout the specification and claims, percentages and ratios are by weight and temperatures are in degrees Fahrenheit unless noted otherwise. When the weight percentage of the alkyl alkoxy sulfate is given it is based on the weight of the ammonium salt. The art recognized terms alkyl alkoxy sulfate, alcohol alkoxy sulfate and alkyl ether sulfate and their derivatives are used interchangeably.